April 16, 2011

Anticoagulant in Pregnancy

Image for display only from [Heart Valve Leakage]

Heparin is the preferred anticoagulant to be used in pregnancy as it does not cross placenta unlike warfarin. Warfarin is associated with risk of fetal embryopathy especially during the first trimester.

However, selection of anticoagulant regime should be individualized based on high risk vs. low risk patient to develop thromboembolism. Heparin has been reported to be failed and lead to serious maternal consequences especially in patient with mechanical heart valve.

Due to that, it has been suggested that inadequacy of heparin to prevent maternal thromboembolism might outweight the risk of warfarin embryopathy during the first trimester.

Three regimes has ben proposed for anticoagulant therapy in pregnancy.

(1) Heparin or LMWH throughout pregnancy;

(2) warfarin throughout pregnancy, changing to heparin or LMWH at 38 weeks’ gestation with planned labor induction at ≈ 40 weeks; or

(3) heparin or LMWH in the first trimester of pregnancy, switching to warfarin in the second trimester, continuing it until 38 weeks’ gestation, and then changing to heparin or LMWH at 38 weeks with planned labor induction at 40 weeks.


1) Target INR is 2.5-3.5. Risk of bleeding is high if INR 4 and accelerated if INR is five. If patient on warfarin, few option available if high INR which is either lower the dose of warfarin, stop the warfarin until INR reach target or use oral/IV vitamin K depending on patient condition and risk for severe bleeding. Using of vitamin K achieve faster effect but resistant to the next dosage of warfarin may persist up to 1 week.

2) Higher risk patient especially on first generation mechanical valve require warfarin throughout pregnancy as it is outweight the risk for fetal embryopathy.

3) Review of 22 children of mothers taking warfarin during prefnancy revealed no significant difference when compared with controls. This finding suggest that the incidence of abnormalities may be lower than previously reported. [Micael A. Belfort et al, 2010]

4) The risk for pregnancy complications in patients treated with sodium warfarin is higher when the mean daily dose exceeds 5 mg.(Cotrufo et al, 2002)


1) Jack Hirsh, Valentin Fuster, Jack Ansell and Jonathan L. Halperin, "American Heart Association/American College of Cardiology Foundation Guide to Warfarin Therapy", Circulation, 2003;107;1692-1711

2) Uri Elkayam, Norbert Gleicher, "Cardiac Problems in Pregnancy 3rd edition", Wiley-IEEE, 1998

3) Michael A. Belfort, George R. Saade, Michael R. Foley et al, "Critical Care Obstetrics", John Wiley and Sons, 2010.

4) Maurizio Cotrufo, Marisa De Feo, Luca S. De Santo, et al, "Risk of Warfarin During Pregnancy With Mechanical Valve Prostheses", The American College of Obstetricians and Gynecologists, Vol 99 No 1, Elsevier Science Inc, January 2001

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